A family of noncentrosymmetric alkali-metal bismuth selenite fluorides, A₂Bi₂(SeO₃)₃F₂ [A = K(1) and Rb(2)], has been synthesized through a mild hydrothermal method. These isostructural compounds all had one-dimensional [Bi₂O₉F₂] chains, which were further connected with neighbouring chains through bridged selenite groups to construct the 3D framework. Because of the relatively ordered alignment of [BiO_xF_y] and SeO₃ groups, they have large second-harmonic generation (SHG) responses of about 15.0(1) and 14.4(2) times that of KH₂PO₄ (KDP) under 1064 nm laser radiation and 0.40(1) and 0.36(2) times that of AgGaS₂ (AGS) under 2.05 μm laser radiation, respectively. In addition, the SHG response of (1) was the largest among those of all reported metal selenites. In addition, all of them had high thermal stability (∼400 °C), wide energy band gaps (over 3.72 eV), and an excellent IR transparent region, suggesting that they had great potential as high power mid-infrared nonlinear optical crystals.

中文翻译：

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A ₂ Bi ₂（SeO ₃）₃ F ₂（A = K和Rb）：具有出色的SHG响应和大的带隙的出色的中红外非线性光学材料

通过温和的水热法合成了一系列非中心对称的碱金属亚硒酸铋铋氟化物，即A ₂ Bi ₂（SeO ₃）₃ F ₂ [A = K（1）和Rb（2）]。这些同构化合物均具有一维[Bi ₂ O ₉ F ₂ ]链，这些链通过桥连的亚硒酸酯基进一步与相邻链连接，从而构建3D骨架。由于[BiO _x F _y ]和SeO ₃基团的排列相对有序，因此它们具有约15.0（在1064 nm激光辐射下分别是KH ₂ PO ₄（KDP）的1）和14.4（2）倍，在2.05μm激光辐射下分别是AgGaS ₂（AGS）的0.40（1）和0.36（2）倍。此外，在所有报告的金属亚硒酸盐中，（1）的SHG反应最大。此外，它们均具有较高的热稳定性（约400°C），较宽的能带隙（超过3.72 eV）和出色的IR透明区域，表明它们具有作为高功率中红外非线性光学晶体的巨大潜力。